1. Field of the Invention
This invention pertains to electrical switches for switching high voltage, high current sources. More particularly, this invention pertains to switches used in high voltage, high current applications as the switching of energy sources used to pump pulsed gas discharge lasers.
2. Description of the Prior Art
Spark gap switches, railgap switches, and other multichannel switches have been used in the prior art to connect a high voltage, high current energy source to a load such as a pulsed gas discharge laser. For use with such lasers, the switch must operate to connect suddenly a high voltage, high current source to the load and the switch must provide a low impedance path for the current.
FIG. 1 depicts a railgap switch that has been used in the prior art with pulsed gas discharged lasers. A blade (1) having a rectangular cross section, typically of 1/2 inch by 1/16th inch in size, and a length of 50 centimeters or so, is mounted adjacent to, but separated from, a second electrode, commonly referred to as the plane (2), having a somewhat larger cross section than the blade and being of approximately the same length as the blade. The space or gap between the blade (1) and the plane (2) is filled with a gas (3) contained by enclosure (4) which enclosure is made out of non-conducting material.
In the prior art, capacitor (5) is charged to a high voltage by high voltage source (6). The side of the capacitor (5) that is connected to high voltage source (6) is then suddenly shorted to ground by thyratron (7) which causes the charge and voltage on capacitor (5) to be placed suddenly across blade (1) to ground. In the prior art, the high voltage causes the gas (3) within enclosure (4) to break down and form multiple conducting paths between blade (1) and plane (2), which conducting paths, in effect, short the switch and connect the voltage and charge on capacitor (5) across laser (8), to ground thus causing the charge on capacitor (5) to discharge in a short period of time through gas discharge laser (8).
In the prior art device, when the voltage between blade (1) and plane (2) exceeded the breakdown voltage of the gas, the statistical processes associated with the breakdown of the gas caused undesirable variations or jitter in the timing of the breakdown of the gas and in the timing of the effective closure of the switch. Various triggering schemes have been used to reduce the temporal jitter in the switch closure. For instance, auxiliary spark discharges have been used to generate ultra-violet radiation, which, in turn, tends to trigger the breakdown of the gas when the voltage between the plane and blade is comparable to, but less than, the self-breakdown voltage of the gas. Auxiliary lasers which inject laser energy into the gas (3), also have been used for this purpose. These prior art methods, however, suffer from electrode erosion in the case of auxiliary spark gaps, and from complexity in the case of auxiliary lasers.